/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.predictionio.controller

import org.apache.predictionio.core.BaseEngine

import scala.language.implicitConversions

/** Defines a deployment that contains an [[Engine]]
  *
  * @group Engine
  */
trait Deployment extends EngineFactory {
  protected[this] var _engine: BaseEngine[_, _, _, _] = _
  protected[this] var engineSet: Boolean = false

  /** Returns the [[Engine]] of this [[Deployment]] */
  def apply(): BaseEngine[_, _, _, _] = {
    assert(engineSet, "Engine not set")
    _engine
  }

  /** Returns the [[Engine]] contained in this [[Deployment]]. */
  private[predictionio]
  def engine: BaseEngine[_, _, _, _] = {
    assert(engineSet, "Engine not set")
    _engine
  }

  /** Sets the [[Engine]] for this [[Deployment]]
    *
    * @param engine An implementation of [[Engine]]
    * @tparam EI Evaluation information class
    * @tparam Q Query class
    * @tparam P Predicted result class
    * @tparam A Actual result class
    */
  def engine_=[EI, Q, P, A](engine: BaseEngine[EI, Q, P, A]) {
    assert(!engineSet, "Engine can be set at most once")
    _engine = engine
    engineSet = true
  }
}
